<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .box {
        width: 0;
        height: 0;
        /* border: 20px solid #f00; */
        border-top: 22px solid transparent;
        border-right: 8px solid #000;
        border-left: 0px solid transparent;
        border-bottom: 0px solid transparent;
      }
    </style>
  </head>
  <body>
    <div class="box"></div>
  </body>
</html>
